1. Field of the Invention
The invention relates to a phase change memory device and method for fabricating the same, and more particularly to a phase change memory device with relatively higher device density and a method for fabricating the same.
2. Description of the Related Art
A phase change memory (PCM) device may potentially serve as a 64-megabyte (MB) or greater stand-alone non-volatile memory. Before PCM devices become a mainstream replacement for flash memory, however, they must first achieve excellent electrical and thermal performance. Fabrication of non-volatile memory with relatively higher device density using the conventional fabrication process is, thus, a major aim of researchers.
U.S. Pat. No. 6,501,111 issued by Intel Corporation discloses a conventional three-dimensional PCM (3D-PCM) 212 with a cup-shaped bottom electrode 206 as shown in FIG. 1a. A contact area between a phase change material 207 and a bottom electrode can serve as a contact area between the phase change material 207 and a width of the cup-shaped bottom electrode 206, thus, device density can be increased. A bottleneck occurs, however, when minimizing the device area during a conventional fabrication process, thus, such a process is unsuitable for a photolithography process with a critical dimension (CD) below 0.1 μm. EP Pat. No. 1339111 issued by ST Microelectronics (STM) Corporation discloses a PCM formed by filling a phase change material into a contact hole 57 with a nano-level CD or a minitrench 58 to reduce the contact area 58 between the phase change material and a cup-shaped heating electrode 22, thus, higher device density can be achieved. If the CD of the contact hole is too small to be filled with phase change material, however, a seam problem occurs.
A PCM device with a higher device density, not limited by photolithography resolution is thus desirable.